1. Field of Invention
This invention relates to fish protection apparatuses for water intakes. More specifically, this invention relates to protecting fish from injury and death resulting from fish entry into water intakes or from fish impingement upon intake screens intended to prevent fish from entering water intakes. This invention protects fish by safely preventing their entry into water intakes and diverting the fish to a selected safe release location.
2. Description of the Related Art
A variety of water users associated with power generation, industrial processes, potable water supplies, and agricultural developments divert water from natural and man-made fish habitats such as oceans, lakes, rivers and reservoirs. Water is diverted through water intakes to uses such as hydroelectric turbines, thermal power plant cooling systems, irrigation canals, industrial water uses, municipal water supplies, and desalination plants.
Water intakes exist in a variety of structures such as canal headworks, pump screenwells, towers, turbine intakes, and penstock intakes. Depending upon the particular site of interest, water intakes may divert water for a solitary system use or for a multiple system use. An example of the latter is four proximate penstock intakes drawing water from a reservoir to supply different turbine units.
Absent intervention for fish protection, fish may enter a water intake and be killed by the process that uses the diverted water. For example, fish entering some hydroelectric turbines may have mortality rates approaching one hundred percent. Fish entering other types of water intakes may also experience mortality rates of one hundred percent due to fish impingement on screens or due to fish entrapment in noninhabitable environments.
Safe passage of fish around hydroelectric projects, specifically hydraulic turbines which can cause injury and death, has for many years been the focus of extensive research. Unfortunately, those research efforts have resulted in the development of relatively few systems or devices which can be applied to reduce turbine passage of fish to a level sufficiently low to meet criteria set forth by state and federal fishery resource managers. Today, the potential negative impacts of fish passage through turbines remains a major unresolved issue in the licensing of the United States' existing and proposed hydroelectric developments. Therefore, a need remains for the development of an effective means to protect fish and thereby protect an economically and socially important natural resource.
Moreover, there is increasing recognition of a need to protect fish from entry into water intakes for diversions of various types in addition to water intakes for diverting water for hydroelectric turbines. However, current technologies, which are adapted specifically to meet the needs of hydroelectric turbines, are not necessarily well suited for water intakes for other types of diversions.
Fish protection apparatuses generally fall within one of four categories, based upon their mode of action. These categories are behavioral barriers, physical barriers, collection systems, and diversion systems. Behavioral barriers use natural behavior patterns to attract or repel fish. The latter three categories may employ screens of different designs. Physical barriers physically block fish passage. Collection systems actively collect fish for return to their original environment. Diversion systems divert fish to bypasses for return to their original environment. The present invention is a water intake fish diversion apparatus that relates to fish diversion apparatuses.
Fish protection apparatuses using screens suffer from the shortcoming of fish impingement which causes injury and mortality. Currently available fish diversion apparatuses employing screens which are acceptable to resource management agencies rely on low flow velocities, 0.4 to 1.0 feet per second ("fps"), to achieve minimal injury and mortality. A requirement for low water velocities may result in a fish protection apparatus which is not cost-effective; for example, high capital costs for the intake structure and less efficient electric power generation.
An existing diversion apparatus is shown in U.S. Pat. No. 4,526,494 entitled PENSTOCK FISH DIVERSION SYSTEM, hereinafter referred to as the "Eicher Penstock System." A penstock is a conduit, generally cylindrical and several feet in diameter, for conducting water. The Eicher patent discloses a fish diversion screen for a penstock supplying water to a hydroelectric turbine. The Eicher Penstock System utilizes existing cylindrical penstock walls as a water passage for water flow through a fish diversion screen. In one of its embodiments, two curved screens are employed, joined together along common linear edges while another embodiment employs a single elliptical inclined plane screen. For purposes herein, an inclined plane is defined as a plane that makes an oblique angle with the plane of the earth's horizon. The Electric Power Research Institute (EPRI), the assignee of the present application, conducted tests of the Eicher Penstock System at the Elwha Hydroelectric Project in Washington State during 1990 and 1991. The results of that testing indicate that the Eicher Penstock System can effectively divert salmonids in penstock water flow at high velocities to a bypass thereby substantially eliminating fish passage through a turbine.
While effective at the Elwha site, the Eicher Penstock System has several limitations. Employment of the Eicher Penstock System is limited to hydroelectric projects having penstocks. The Eicher Penstock System is not useful for water intakes other than penstocks such as those for pump screenwells, canals, and so forth. Use of existing penstock walls limits adjustment of water flow into the Eicher Penstock System and within the Eicher Penstock System while such adjustment may be required to provide a biologically effective diversion apparatus. The interior of a penstock is a difficult access location for repair and maintenance due to the difficulty in dewatering the fish diversion screen. A penstock location makes it difficult or impossible to bypass a fish diversion screen during periods when the screen's use is not necessary, for example, during periods of low fish migration activity. Location of a fish diversion screen in a penstock also creates difficulty in configuring a fish bypass for adjustment of the desired bypass velocity at headpond water levels since the penstock flow to its hydraulic turbines defines bypass flow rate. Finally, the Eicher Penstock System does not feature advantages presented by modularity since its penstock location limits to only one the number of Eicher Penstock Systems which may be used for a given penstock.
The limitations of the Eicher Penstock System inspire a need for an apparatus designed for use at the many hydroelectric projects which do not incorporate penstocks as well as designed for use at water intakes other than those for hydroelectric projects. The inventors of the present invention have developed a novel, modular fish diversion apparatus designed for application at hydroelectric sites which do not have penstocks, at sites where penstock application would not be cost-effective, and at sites which are water intakes for non-hydroelectric water uses. The apparatus safely diverts downstream migrating fish and reduces turbine injury and mortality of fish species which do not migrate. The compact nature of the apparatus, which is designed to function at relatively high water velocities, results in a substantial cost savings over conventional forebay screening apparatuses, such as travelling screens, in most applications. The apparatus is particularly suitable for retrofitting at sites where space limitations preclude installation of conventional screening apparatuses.